It is well known that molybdenum provides enhanced fuel economy when used in lubricants for gasoline or diesel fueled engines, including both short and long term fuel economy (i.e., fuel economy retention properties). The prior proposals typically use molybdenum at levels greater than 350 ppm up to 2,000 ppm in additive packages, which contain one or more detergents, anti-wear agents, dispersants, friction modifiers, and the like.
The present inventors have found that fuel economy and fuel economy retention properties can be improved to meet the requirements of the next generation of motor oil certification such as the proposed ILSAC GF-3 standards (International Lubricants Standardization and Approval Committee), without the use of molybdenum which is commonly used in conventional additive packages, thus providing a less expensive lubricating oil composition.